A semiconductor device includes a plurality of layers on a silicon substrate. The layers are deposited on the substrate through a deposition process. The deposition process has several important issues that are important to evaluate the deposited layers and select a deposition method.
First, one example of the important issues is ‘quality’ of each of the deposited layers. The ‘quality’ represents composition, contamination levels, defect density, and mechanical and electrical properties. The composition of the deposited layer may be changed according to deposition conditions. This is very important to obtain a specific composition.
Second, another example of the issues is a uniform thickness over the wafer. Specifically, a thickness of a layer deposited on a pattern having a nonplanar shape with a stepped portion is very important. Here, whether the thickness of the deposited film is uniform may be determined through a step coverage which is defined as a ratio of a minimum thickness of the film deposited on the stepped portion divided by a thickness of the film deposited on the pattern.
The other issue with respect to the deposition may be a filling space. This represents a gap filling in which an insulating layer including an oxide layer is filled between metal lines. A gap is provided to physically and electrically isolate the metal lines from each other.
Uniformity is one of the important issues related to the deposition process. A non-uniform film may have a high electrical resistance on the metal line to increase possibility of mechanical damage.